15min:

ANATOLY DZHONSON, EVAN B. JOCHNOWITZ, EUNSOOK KIM AND JOHN P. MAIER, Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland.

A new approach has been developed for the purpose of measuring electronic transitions to bound excited states for cations that have been collisionally relaxed to low vibrational and rotational temperatures ( 25 K). This has been used to obtain the first gas phase spectra of three new polyacetylene cation chains (HC₁₂H⁺, HC₁₄H⁺, and HC₁₆H⁺) as well as two different protonated species (HC₆H₂⁺ and HC₈H₂⁺) using a two-color ion-photodissociation approach applied to ions held in a 22-pole trap. Specifically, the origin bands of the A ² - X ² electronic transitions of HC₁₂H⁺, HC₁₄H⁺, and HC₁₆H⁺ were located at 10811, 9333, and 8739 cm^-1, respectively, while the B ¹A₁ - X ¹A₁ transitions of HC₆H₂⁺ and HC₈H₂⁺ ( C _2v geometry) were recorded at 26404.0 and 21399.8 cm^-1.